Both tries were converted by Te Atawhai Mason for a 14-12 turnaround.
"Wesley then applied concerted pressure through their large pack and squeezed over for a converted try right on half time to take the lead again 19-14," said Simpson.
"The half time talk was to keep the ball, be patient and move the Wesley forwards around, which WCS did effectively scoring two more converted tries."
Halfback Adam Lennox crossed and then Osamu got his double off a set up by first-five Harry Godfrey, both converted by Mason.
Down 28-19 with 20 minutes left, Wesley replied quickly with a break away try down the wing in the corner, closing the gap to four points.
"As the Wesley pack was tiring, they managed to roll out two even bigger forwards to rumble the ball up the field," said Simpson.
"With four minutes to go they got to within 5m of the WCS try line.
"After outstanding defence by the whole team, which included holding them up over the line twice and defending several scrums and tapped penalties, Wesley managed to squeeze over in the last minute of the game to score a converted try."
Simpson said every player gave his all.
"Leo Allan having another strong game on defence, Tom Pease competing with boys more than 50kg heavier and Sione Osamu having his best game of the season against a lot of his Tongan compatriots."
Collegiate's next game is away to St John's in Hamilton on Saturday, with a 12pm kickoff.